i agree with the walking onions and asparagus, no one mentioned Jerusalem Artichokes, never saw a higher yielding perennial. also Daylillies are quite high yielding and mallows, violets, good for salads..and quite prolific.
I believe lambsquarters is an annual but it reseeds and is quite high yielding.
and then there are
fruit and nut
trees which are perennial and generally are very very high yielding, berries and grapes as well. they do take a while to start providing but once they do they last a long time..but never hurts to plant their replacements in advance as well.